Answer:
3
Explanation:
Here's the balanced equation;
C2H4 + 3O2 → 2CO2 + 2H2O
C ⇒2 C ⇒1 x 2 = 2
H ⇒4 H ⇒2 x 2 = 4
O ⇒3 x 2 = 6 O ⇒ (2 x 2) + (2 x 1) = 6
Answer : The mass of helium gas in the balloon is, 1.23 grams.
Explanation : Given,
Volume of helium gas = 6.9 L
First we have to calculate moles of helium gas at STP.
As we know that, 1 mole of substance occupy 22.4 L volume of gas.
As, 22.4 L volume of helium gas present in 1 mole of helium
So, 6.9 L volume of helium gas present in
of helium
Now we have to calculate the mass of helium gas.

Molar mass of He gas = 4 g/mol

Thus, the mass of helium gas in the balloon is, 1.23 grams.
Moles of Lithium phosphate : 0.495
<h3>Further explanation</h3>
Given
6 Li + Zn₃(PO₄)₂ ------- > 2 Li₃PO₄ + 3 Zn
Required
Moles of Lithium phosphate
Solution
moles of Zinc(Ar=65,38 g/mol) :
= mass : Ar
= 48.6 : 65.38
= 0.743
From equation, mol ratio of Zn : Li₃PO₄ = 3 : 2, so mol Li₃PO₄ :
= 2/3 x mol Zn
= 2/3 x 0.743
= 0.495